Ok so I'm thinking of building a AR pistol in 10"
My goal is to make a 10" that I can use as a defense and light hunting of deer maybe out to 300 max.
I was originally thinking of 5.56 because it's so easy to come by and I see me shooting a lot for plinking fun with it.
I figured the 5.56 would be ok out to 300, but I also started thinking about the 300BK. I am already set up to reload it and for defense and deer size game it would be much better than 5.56. (Also in my state the 5.56 would probably fall short. I believe they have a 6mm or 6.5mm limit, but I haven't checked it in awhile)
Anyway aside from the cost of ammo, how does the 300BK shoot from the 10" barrels and what kind of range would it get with 120gr or so bullet?
Thanks for any input.
SS33

I would get both.  Seriously the parts market is priced low enough you can have two uppers or two guns.

223 for inexpensive shooting.
300 blackout for hunting.

Be careful and clear about marking uppers so you know what rounds to use in each.

unless you reload 300 is not inexpensive to plink with.

For me 5.56mm or 300BLK is fine for hog hunting, but for deer I would step up to a 308/7.62x51mm. Might be able to get away with a 6.8mm round for deer with a longer barrel and if you shoot at a short distance. Short barrels are great for home defense, but not my first choice for hunting. I prefer longer barrels for more velocity for hunting. I grab my bolt action 308 for deer. I grab my AR-15 for hogs and home defense.

I would keep any hunting shots inside of about 150 yards with the blackout if that helps you choose.  Nothing wrong with having both.

If you plan on suppressing it then Id say 300. If not stick with 223/5.56.  The concept of 300 blackout is to suppress it not just to say "I have it." Go silent or go 5.56.

I have a 6.8, but my state only has a handgun season no rifle.  If I really needed to I can use a 308 for anything longer.
I was looking for something I could "maybe" hunt pistol and for sure a defensive weapon because of size and also the ability to carry CCW in my car.(FHTF type backup)
I already have an older(pre BLACKOUT) 16" 300 Bk.
I was thinking of doing both, but really wanted to decide on my 1st since I'm doing one at a time. I'm thinking 5.56 because of convenience of ammo, but I guess I'm looking for a reason to make the 300BK my 1st choice.
Does anyone have drop data for 300bk vs 5.56 in a 10"?
Also interested in energy for the 10"
I did think about a 7" 5.56 and a 10" 300BK
Not sure I like the pistol length gas system in the 7" for the 5.56 though. I've heard they can have issues and there is a big velocity loss?

they both have trade offs, I settled on a 10.3 556 for accessibility and I already reload a big variety , I don't hunt with it but I would with some TSX or other quality projectile no question and a good distance too.

many hungry people are successful with 22 mag in theses parts......shot placement is king get the caliber you want and master it

300 yard shots on deer with .300 is going to be pushing it a bit.   Ranging error will mess you up, and I'd want a 12"or longer barrel.

Cut that distance in half - which is entirely reasonable over in the Eastern US - and you're fine.



It's worth pointing out that the .300 isn't just about suppression.   It gives you ballistics not that far off from a .30-30 or 7.62x39 out of a very short barrel without having function issues or obnoxious muzzle blast.

I'll toss in my vote for "get both".   I wouldn't get a 10" for each, that's a bit of a waste of the properties of each caliber.    I'd suggest 8.3 - 9" for the .300 and 11.5-12.5" for the 5.56.    A basic iron-sighted 5.56 upper can be had for very little money.   The money you save plinking with 5.56 will pay for the upper pretty quickly.

Realistically it will be a 200 yard and in gun with the majority(90%) 100 and under.
The hunting is just a side note, it would not be my  go to for hunting. looks like both at 300 yards will be under 15" drop so it's still workable.
Is the 300bk not as sensitive to barrel length as the 556?
I have heard that it's not affected by barrel length as much (aka doesn't drop energy) as quickly due to it's mass vs the 556, but I haven't really seen any comparison tables for pistol length barrels?

Thanks for all the input guys it has given me for to think about.

I went through the same dilemma and after researching for about a month, I ended up ordering a 10" 300 blackout upper from Andro Corp. They currently have 25% off for labor day and I was able to get an upper with a ballistic advantage barrel minus BCG and charging handle for about $270 shipped.

Awesome value for me to try 300 blackout with a quality upper.


This chart might help for comparison.

yea I wondered across this chart earlier.  This is good for showing muzzle energy vs barrel length. Next I need to find a bullet drop chart for about the same 2 bullets.
Thanks for the info. I'm looking at Faxon barrels right now since they are local and I've been wanting to try one out.

Not sure of any 223 bullet I would trust to hunt with out to 300 yards out of a 10" barrel.  300blk on the other hand....

The Barnes bullet in 300blk is a good combo. It's very accurate in my 8.5" pistol. If you hunting deer a 6.8 SPC would be a good choice too.

I don’t think I would attempt to shoot a deer out to 300 yards, in my opinion it’s hard to get a clean shot at that distance. I have a 8.5” 300blk and with my Hornady SST handloads I can shoot sub 2” groups at 100 yards with iron sights. I’m with GunDisaster, I would get both. Even if you have one lower receiver and two uppers, you would have the best of both worlds, cheap plinking with 5.56 and a harder hitting round for home defense and hunting.

Don't look at it from a caliber perspective - if 300m is a goal, then what cartridge will deliver 1,000 foot pounds of force, the ethical limit, that far? Not anything you can shoot effectively from a 10" barrel. It's a simple ballistics exercise.  

For that matter shooting deer at 300 is problematic regardless of cartridge. I started out with that in mind, years ago, with .308, then moved to .30-06, tried .30-30, 6.8SPC - and then sat down to really think it thru.

I had been hunting one particular section of public ground for 40 years, and on one of those rarer mornings while still awake I plotted every known kill I had knowledge of where I knew the location of both shooter and game. Most were shots under 80m. That coincided with verbal testimony of the shooters, too, and also corroborated what I had seen elsewhere or in other tales of legendary hunting prowess. The bulk of the shots aren't long distance, they are actually 25-80m.

First, because the hunters put themselves in that range where deer traveled. Second, they simply couldn't see any further due to cover. Deer in rut tend to hold close to cover during the season.

I then checked to see how far 5.56 would hold at least 1,000 foot pounds of force and 80m is the limit. It is extended for larger bullets, of course, but most won't carry 1,000 foot pounds past 125m from a ten inch barrel. They don't start high enough to keep the energy - and the larger bullets also drop sooner. You do get more power and an incremental extension of range but 300 is too far for ethical hunting purposes, IF you could even get the shot.

I built an AR in 5.56 for close in hunting and use 70 gr OTM for ammo. If shots longer than that were part of the plan, then 6.8, .30-30, or .30-06 would be the better choice - I sold off the .308's long ago as cheap surplus dried up in the '90s. 5.56 hasn't, tho, and I picked up boxes of Tula just the other day retail at 5.99.

I will never find 6.8 or .300BO at those prices, and the marginal difference in range hunting deer will be a small incremental change - one that only extends a shot into even deeper cover where I can't see any movement anyway without a scope. That means 2-4 power on top of what I built as an iron sights HD gun which inside a home will primarily use a 25 foot lighted point for aiming.

It becomes an exercise in contradictory purposes trying to build a 300m deer gun that serves as an SBR for HD. Especially since the ballistics just aren't there.

Considering the bullet drip of .300BO at 300m, I wouldn't consider it at all and choose something flatter shooting anyway. Again, it's not about one vs another, it's about defining your range and target then choosing a cartridge that actually fits. Given a ten inch barrel - nothing will do that job effectively. It's not what an SBR does, at all.

80-100m is the practical and ethical limit for an AR with 10" barrel - and just about any cartridge you pick will do that. I picked 5.56 because it saved me $300 buying another upper and that money can go to ammo or accessories. Plus - I will likely not ever Kaboom the 5.56 because a stray .300BO got in a magazine.

More info
http://300aacblackout.com/

The blackout is similar to the old 30/30. But, we now have better bullets. If you hunt close, it will do fine. I am waiting on my suppressor, and it will be my short range gun.

I have SBRs in 10.5" 5.56 and a 7.5" BLK I prefer the blackout for plinking and hunting. I have 125gr Sierra SP Supers that take deer very well. So far The longest was 90yds, of the four I have taken with the BLK all dropped where they stood with the exception of one and she jumped once and was out.  I load subsonics for plinking. lower recoil and blast, the 10.5" 5.56 is a tool, I train with it but she remains on standby - too much muzzle blast for plinking. I think a 10ish inch 300 blk will serve you well but I would highly recommend reloading for it.

I have tons of blackout brass, so I doubt I would but any loaded ammo because of the price.
I am leaning toward a 10" 5.56 AND a 7.5" blackout at this point. But they will build separate. Unless I sell my 16" blackout upper to fund some of this adventure. I really can't afford to build 2 with holiday season around the corner. So which to build 1st?

7.5" 300 for the win

I was looking at an 8.5" 300AAC for mine.  I have a 10.5" .223 Wylde now and it is wonderful.

Interesting choice of chambering. Wylde. I prefer the wylde for my rifles.

Pewpewpew,
I said I have the brass. I also have a lot of 223 loaded ammo

Still debating ??
However it will be a 7.5" if I do 300 1st??

Use a Nosler Partion 60 grain or a Sierra 65 Game king or one of the Barnes bullets and keep within a hundred yards and no problem. I will be 65 next spring. Been hunting deer since 1964 and I shot one deer at 200 yards. It was a measured shot with my Marlin 45/70 guide gun and I had figured out the trajectory. Any onther deer was under a hundred yards. Most under 50.,For those ranges a 223 will work just fine. I killed more than a few deer with a 22 mag pistol. All drt. Bullet placement is the key.

good post based on experience
I got a small fork once at 40 or so yards with a mini14 , 55gr soft points nothing special and I was surprised at the damage .....dead before he hit the ground .

this Barns53grTSX was shot into water jugs at 100 yards , 10.3" , 2773 fps


same barrel, same yards, 77gr hpbt, 2318fps

Good info.  I enjoyed reading all the different points of view

you guys are hunting with your AR pistols? I guess I didnt even think about it but is it legal?

BTW I ended up going 300BK 1st. Then building a 5.56. But my 300BK is my baby now.  I took it to the range today and shot 50 to 200 yards with it. Not bad at all with a red dot.
It's becoming my GTG.
I reload and I've scored some good deals on brass and bullets lately.
I love my 300BK pistol. The 5.56 not as much. louder, more flash and seems to be more kick unless I'm using full power 300bk.
Both are nice and I would trade either, but my pick it he 300BK.  It's just sooo much fun.

Nice. I just 'ended up' with a CHF PSA 5.56 setup and, I don't think I'll ever use it. I've got so much 300 BLK supplies I just don't see a reason.

The only thing I could think of is 300 blk out might dry up quicker and longer than 5.56 should there be an extended shortage. That would only hurt for the fun factor though. I would still have a stockpile for defense as I don't shoot that stuff.

My problem is my fiance decided she liked it and wants to claim it as hers. You know how that works
I'll probably have to make another one for me now